Compressive Preloads Research Articles

Impact analysis of compression preloaded honeycomb sandwich structures

Honeycomb cores made of phenol resin impregnated paper are widely used in sandwich structures of aircraft. Owing to the rather weak core material, this kind of sandwich is prone to a range of damages as a result of impact loading which may accidentally occur during operation. When employed in aircraft these structures have to be damage tolerant. This means barely visible damages have to be considered in the structural design process. In the standard design process for damage tolerant aircraft structures especially the effect of impacts has to be considered but is mostly investigated on unloaded sandwich components. However, aircraft structures are not completely stress free, even when the aircraft is in parking position. At least the structural weight will cause a permanent static preload. In the literature there are only few investigations dealing with the impact behaviour of preloaded honeycomb sandwich structures. In general, studies on composite structures have shown that tension preloads lead to higher structural impact resistance, while prestressing in compression reduces mechanical properties such as impact strength and stiffness of the structure. For this reason, a compression preload is considered as the more critical load case. In order to evaluate the effect of static compression preloads an experimental study on five different honeycomb sandwich configurations was conducted. The experimental investigations showed that even low preloads cause a higher structural damage area, which results in a lower residual strength of the structure. The results indicated that it is recommendable to consider structural compression preloads in the aircraft structural design process.

Design and Biomechanical Evaluation of a Bidirectional Expandable Cage for Oblique Lateral Interbody Fusion

Oblique lateral interbody fusion (OLIF) surgery is a minimally invasive spinal surgery technique that has become increasingly popular in recent years. The primary objective of the current study was to design a minimally invasive expandable fusion device that can reduce iatrogenic nerve damage and minimize endplate damage during OLIF surgery, while restoring intervertebral height and alignment. The second objective was to use finite element analysis to evaluate the biomechanical stability of the newly designed expandable fusion device after implantation into the intervertebral space. A new bidirectional expandable cage was designed in this study. A finite element model (FEM) of L3-L5 lumbar segment was modified to simulate decompression and fusion. The modified FEMs were constructed in the following cases: intact model, bidirectional expandable cage (alone, with unilateral pedicle screws [UPSs], and with bilateral pedicle screws [BPSs]) model, conventional OLIF cage (alone, with UPSs, and with BPSs) model. To simulate physiological loadings, the models were subjected to a follower compressive pre-load of 400 N, in addition to 8.0 Nm of flexion, extension, lateral bending, and axial rotation moments. All modified FEMs exhibited a significant reduction in motion at L3-L5 compared to the intact model. Among the fusion models, the bidirectional expandable cage (BEC) with BPS model displayed the highest stiffness and demonstrated a reduced range of motion (48.5%-75.7%). Additionally, the peak stress on the endplate in the conventional OLIF cage (Conv-OLIF) model was generally lower than that in the BEC models. The cage in the BEC ALONE model exhibited the highest stress (93.87-176.3 MPa) on the endplate in most motion modes, while the cage in the Conv-OLIF+BPS model had the lowest stress (16.67-30.58 MPa) on the endplate in most motion modes. The maximum stress on the fixation in the BEC fusion models was generally lower than that in the Conv-OLIF fusion group under the same loading conditions. The OLIF ALONE model had the lowest stress on the adjacent disc, while the stress level in the BEC ALONE model was very close to it. The BEC implanted models had higher stiffness, and more proper stress distribution on the posterior fixation was comparable to that of the Conv-OLIF models. However, the endplate stress peaks and cage stress peaks of the BEC models were slightly higher than those of the Conv-OLIF models, though still within a clinically acceptable range. Taking into account both biomechanical and clinical perspectives, BEC-assisted unilateral pedicle screw fixation meet clinical demand and may serve as a viable alternative to Conv-OLIF fusion.

Suction contribution to uplift capacity of suction buckets under serviceability conditions

Suction pressures induced inside buckets under tensile loads can greatly increase bucket uplift resistance. However, a considerable bucket upward displacement is required to mobilize a sizeable part of the suction pressure, which may not meet the serviceability requirements. To address this issue, this study emphasizes that suction buckets operate under compressive preloading conditions owing to their self-weight and potential ballasting, and that reduced compressive preloading can result in suction pressures at the underside of the bucket lid. The critical suction pressure, which refers to the suction pressure under the lid bottom at the instant at which the lid separates from the soil surface owing to tension, was identified and considered to contribute to the bucket uplift capacity. An axisymmetric consolidation model was developed to quantify the critical suction pressure. Analytical solutions were obtained using integral transformation techniques and verified using published data. A detailed parametric study was then conducted to explore the effects of bucket and soil parameters on the critical suction pressure. The results indicated that the critical suction pressure was robust despite significant variations in the soil permeability and boundary drainage conditions. This study provides new insights into the serviceability-driven design of suction buckets subjected to tensile loads.

The Effect of Compressive Preload on the Work Produced by Cu–Al–Ni Single Crystals in the Course of Burstlike Recovery of Shape-Memory Strain

The Effect of Compressive Preload on the Work Produced by Cu–Al–Ni Single Crystals in the Course of Burstlike Recovery of Shape-Memory Strain

A Novel MRE Adaptive Seismic Isolator Using Curvelet Transform Identification

Magnetorheological elastomeric (MRE) material is a novel type of material that can adaptively change the rheological property rapidly, continuously, and reversibly when subjected to real-time external magnetic field. These new type of MRE materials can be developed by employing various schemes, for instance by mixing carbon nanotubes or acetone contents during the curing process which produces functionalized multiwall carbon nanotubes (MWCNTs). In order to study the mechanical and magnetic effects of this material, for potential application in seismic isolation, in this paper, different mathematical models of magnetorheological elastomers are analyzed and modified based on the reported studies on traditional magnetorheological elastomer. In this regard, a new feature identification method, via utilizing curvelet analysis, is proposed to make a multi-scale constituent analysis and subsequently a comparison between magnetorheological elastomer nanocomposite and traditional magnetorheological elastomers in a microscopic level. Furthermore, by using this “smart” material as the laminated core structure of an adaptive base isolation system, magnetic circuit analysis is numerically conducted for both complete and incomplete designs. Magnetic distribution of different laminated magnetorheological layers is discussed when the isolator is under compressive preloading and lateral shear loading. For a proof of concept study, a scaled building structure is established with the proposed isolation device. The dynamic performance of this isolated structure is analyzed by using a newly developed reaching law sliding mode control and Radial Basis Function (RBF) adaptive sliding mode control schemes. Transmissibility of the structural system is evaluated to assess its adaptability, controllability and nonlinearity. As the findings in this study show, it is promising that the structure can achieve its optimal and adaptive performance by designing an isolator with this adaptive material whose magnetic and mechanical properties are functionally enhanced as compared with traditional isolation devices. The adaptive control algorithm presented in this research can transiently suppress and protect the structure against non-stationary disturbances in the real time.

Effect of Amount of Fibre and Damage Level on Service Life of SFR Recycled Concrete in Aggressive Environment

The paper presents a numerical calculation of the service life of concrete structures considering the effect of chlorides in the case of the material properties of structural lightweight waste aggregate concrete. Different amounts of fibres (0.0%, 1.0%, and 1.5%) and different values of compressive preloading (0%, 50%, and 100% of the ultimate strength capacity-USC) were considered. The subject of the research was the comparison of the influence of the constant diffusion coefficient and the time-dependent diffusion coefficient regarding the service life of the selected structure. Nine groups of material characteristics in combination with two numerical models are compared. A time-dependent diffusion coefficient and maturation coefficient, which were determined based on long-term monitoring (up to 461 days), were accepted for the numerical modelling. Thanks to time-dependent parameters, it is possible to observe the results of the theoretical service life of the structure and the influence of the mentioned factors. The analysed structure can be considered as the upper layer of an industrial floor in a chemical plant. It is important to determine the theoretical service life at which the structure shall be inspected or replaced. The results, in general, show that a higher amount of fibres reduces the service life as well as the preloading of the structure. An exception was a mixture with 1% of fibre loaded to 50% USC, which shows a lower diffusion coefficient than the specimens without preloading.

Experimental Study of Tensile Preloading Influence on the Mechanical Behaviour of Pseudo-Ductile Hybrid Composite under High-Velocity Impact

The hybridisation of fibre-reinforced plastics is one of the perspective technological methods that make it possible to reduce the sensitivity of polymer composites to stress concentration and increase their damage tolerance. In this case, hybridisation means a combination of different types of reinforcing fibres in one yarn, one layer or one package. In most published papers, the authors investigated the mechanical behaviour of hybrid fibre-reinforced plastic under static loading or low-velocity impact conditions only. At the same time, statically preloaded structures made of composite materials can also be subjected to high-velocity impact. Tensile or compressive preloading affects not only the amount of energy absorbed by the composite but also changes the deformation and fracture pattern. This paper presents the results of the experimental study of the mechanical behaviour of a woven carbon/aramid hybrid composite under tensile preloading and high-velocity impact. Pre-tensioned specimens of homogeneous and hybrid composites were subjected to a high-velocity impact by a steel spherical projectile with the velocities up to 900 m/s. The experimental results showed that the hybrid composite had the lowest sensitivity of the ballistic limit to the tensile preloading.

Fire behavior and design of steel columns reinforced by prestressed CFRP strips

This study analyzes the behavior of steel columns reinforced by prestressed (PS) carbon fiber reinforced polymer (CFRP) strips exposed to fire. First, tests are performed to study the CFRP material degradation under high temperatures. The elastic modulus and strength of the CFRP decrease with increasing temperature. Second, a thermal–mechanical coupling analysis is conducted with finite element method (FEM) to study the behavior of composite members exposed to fire. Under compressive preloading, the columns are exposed to the ISO 834 standard fire curve. The fire exposure time of columns with different initial CFRP prestressing forces is obtained. All the specimens fail because of global buckling either due to the slacking of the concave side of the CFRP or the plastic deformation of the steel. Subsequently, parametric studies are performed considering different initial CFRP prestressing forces, preloadings and column slenderness values. Finally, a design method is proposed for steel columns with PS CFRP that are exposed to fire, followed by a design example. Columns with protections can achieve high buckling capacities at room temperature and long fire exposure time.

Biomechanical Changes of Adjacent and Fixed Segments Through Cortical Bone Trajectory Screw Fixation versus Traditional Trajectory Screw Fixation in the Lumbar Spine: A Finite Element Analysis

The finite element method was used to investigate the biomechanical adjustments of adjacent and fixed segments after lumbar fusion and fixation with traditional trajectory (TT) and cortical bone trajectory (CBT) screws. The model used was a validated nonlinearly L3-S1 finite element model. Interbody fusion cages and 2 types of screws were used to work on the L4-L5. To simulate flexion, extension, lateral bending, and axial rotation, all models were loaded in 3 planes with a compressive pre-load of 400 N and a bending moment of 7.5 N/m. Under various loading conditions, the range of motion (ROM), peak Von Mises stress of the vertebral body, stress of the intervertebral disc, stress of the facet joints, stress of the endplate, and stress of internal fixation were compared. In all instrumentation models, the ROM at fixed segments decreased. At adjacent segments, the ROM of the CBT model was greater than that of the TT model. The CBT model had a greater peak Von Mises stress of the L4 and L5 vertebral bodies, as well as greater stress of internal fixation, than the TT model. Furthermore, as compared with the TT model, the CBT model's facet joint and endplate stress were lower at fixed segments but higher at adjacent segments. The stress on the L3-L4 and L5-S1 intervertebral discs in the CBT and TT models, on the other hand, was nearly equivalent. At the fixed section, CBT may provide slightly better stability, endplate tension, and facet joint stress than TT. The greater ROM, endplate stress, and facet joint stress of CBT in adjacent segments, on the other hand, should be taken into account in the future.

Buckling and free vibration of a side-cracked Mindlin plate under axial in-plane load

In this paper, the buckling and free vibration of a Mindlin plate with a side crack are presented considering a uniaxial in-plane compressive or tensile load. The side crack is through the thickness of the plate. In the Ritz method, a series of corner functions are incorporated into the admissible functions which consist of the modified characteristic functions. With this treatment, one can describe the singularity in stress near the tip of the crack as well as the discontinuities in both displacement and bending rotations across the crack. The buckling loads and natural frequencies are solved through eigenvalue problems considering the existence of the crack. The effects of location, length and orientation of the crack on the buckling and free vibration of the loaded plate are demonstrated. The coupling effect of the crack and the in-plane load on the vibrational characteristics of the plate is analyzed with varying parameters. It is shown that the influences of the tensile and compressive preloads are enhanced by the crack, and the tensile preload can cause the low-order frequency to increase with the growing crack.

Investigation into high velocity impact response of pre-loaded hybrid nanocomposite structure

Pre-loaded polymer composite structures subjected to high velocity impact have received little attention compared to the corresponding structure under static impact test. In fact, no report was found on such structures, which incorporate nanoparticles as a secondary reinforcement. The main objective of this research work is to assess the high-velocity impact response of polymer composite plates containing nanoclay under different pre-loads. E-glass woven roving and unsaturated polyester resin were used to prepare composite plates and 1.5 wt% nanoclay was introduced into the resin system. High velocity impact with full perforation as well as impact tests with rebound were conducted via a gas gun in a velocity range of 138–185 m/s. Three types of pre-loading were applied and compared with no pre-load condition, namely: uniaxial compression, uniaxial tension, and biaxial compression/tension hybrid pre-load. The results indicated significant better energy absorption performance by the nanoclay modified specimens under all pre-load conditions compared to the specimens without nanoclay. Results further showed that biaxial compression/tension and uniaxial compression pre-loads are more critical than tension pre-loads. Nanoclay reinforced composite plate showed greater damage extension compared to composite plates without nano reinforcement. Major failure modes identified include delamination, matrix cracking, and fiber breakage.

Biomechanical study of proximal adjacent segment degeneration after posterior lumbar interbody fusion and fixation: a finite element analysis

PurposeTo investigate the biomechanical changes in the proximal adjacent segment with different grades of degeneration after posterior lumbar interbody fusion (PLIF).MethodsWe created three finite element models of the L3–5 with different grades of degeneration (healthy, mild, and moderate) at the L3–4 that were developed by changing the disc height and material properties of the nucleus pulposus. The L4–5 were operated by interbody fusion cages and pedicle screws. All models were loaded with a compressive pre-load of 400 N and a bending moment of 10 N a in three planes to recreate flexion, extension, lateral bending, and axial rotation. The range of motion (ROM), nucleus pressure, and annulus fibrosus pressure of the L3–4 were evaluated.ResultsThe ROM, nucleus pressure, and annulus fibrosus pressure increased at the L3–4 after PLIF. As the degeneration progressed in the L3–4, the ROM of the L3–4 decreased while the nucleus pressure and annulus fibrosus pressure increased.ConclusionsAdjacent segment degeneration (ASD) may be related to the ROM and intradiscal pressure after PLIF. However, as the degeneration of the proximal adjacent segment increases, the ROM in the proximal adjacent segment gradually decreases, but the pressure on the nucleus pulposus and annulus fibrosus gradually increases. Degeneration of the proximal adjacent segment before operation is a risk factor for the ASD after PLIF.

Kinematic assessment of an elastic-core cervical disc prosthesis in one and two-level constructs.

IntroductionAnterior cervical discectomy and fusion has been associated with the development of adjacent segment degeneration (ASD), with clinical incidence of approximately 3% per year. Cervical total disc arthroplasty (TDA) has been proposed as an alternative to prevent ASD.HypothesesTDA in optimal placement using an elastic‐core cervical disc (RHINE, K2M Inc., Leesburg, Virginia) will replicate natural kinematics and will improve with optimal vs anterior placement.MethodsSeven C3‐T1 cervical cadaver spines were tested intact first, then after one‐level TDA at C5‐C6 anterior placement, after TDA at C5‐C6 optimal placement, after two‐level TDA at C5‐C6 and C6‐C7 optimal placement, and finally after two‐level TDA at C5‐C6 lateral placement and C6‐C7 optimal placement. The specimens were subjected to: Flexion‐Extension moments (+1.5 Nm) with compressive preloads of 0 N and 150 N, lateral bending (LB) and axial rotation (AR) (+1.5 Nm) without preload.Results C5‐C6 TDA in optimal placement resulted in a non‐significant increase in flexion‐extension ROM compared to intact under 0 N and 150 N preload (P > 0.05). Both LB and AR ROM decreased with arthroplasty (P < 0.01). Optimal placement of C6‐C7 TDA resulted in an increase in flexion‐extension ROM with preload compared to intact (P < 0.05) while LB and AR ROM decreased with arthroplasty (P < 0.01).ConclusionThis six degree of freedom elastic‐core disc arthroplasty effectively restored flexion‐extension motion to intact levels. In LB the TDA maintained 42% ROM at C5‐C6 and 60% at C6‐C7. In AR 57% of the ROM was maintained at C5‐C6 and 70% at C6‐C7. These findings are supported by literature which shows cervical TDA results in restoration of approximately 50% ROM in LB and AR, which is a multifactorial phenomenon encompassing TDA design parameters and anatomical constraints. Anterior placement of this viscoelastic TDA device shows motion restoration similar to optimal placement suggesting its design may be less sensitive to suboptimal placement.

Qualification of the endurance strength enhancement of silane coated concrete parts

High precision concrete can be used for precision machine parts as a replacement for natural stone to save costs and reduce the lead time (Hahm and Theska 2017 2nd Gas Bearing Workshop (Düsseldorf); Hahm et al 58th Ilmenau Scientific Coll. (Ilmenau); Hahm et al 13th Int. Conf. & Exhibition (Berlin); Berg et al 10th Int. Conf. & Exhibition (Delft)). In contrast to the base frames, moving parts need to have a high specific stiffness thus requiring a lightweight design. To guarantee reliability comparable to steel or aluminum parts, the endurance strength of the concrete parts has to be improved significantly. Reinforcement by implementation of steel or carbon fibers is not applicable since it results in thermal inhomogeneity. As an alternative, reinforcement can be provided by functional coatings. The application of a tailor made sol–gel coating and their effect on the mechanical properties of concrete parts represents the focus of this contribution. Coatings reduce the probability of fundamental damage effect mechanisms by closing superficial pores and cracks and by introducing internal compressive preloads. Additionally, the stiffness improvement due to the coating enhances the parts endurance strength by lowering the effective stress. The experimental results with a primitive specimen geometry and a combination of tensile and flexural tests proves the tendencies for strength enhancement in general different sol–gel compositions were investigated. The mathematical description has been evaluated based on these measurements to validate the influence on the endurance strength. To reduce the uncertainties of the measurements the specimen quality and test machine reproducibility needs a further improvement. A direct deformation measurement of the specimen during the tensile test is required to allow an entire evaluation of the presented model under consideration of skin effects. This way, the developed simulation method for coated machine parts with complex geometry can be fully applied.

The effect of follower load on the intersegmental coupled motion characteristics of the human thoracic spine: An in vitro study using entire rib cage specimens

The mechanical coupling behaviour of the thoracic spine is still not fully understood. For the validation of numerical models of the thoracic spine, however, the coupled motions within the single spinal segments are of importance to achieve high model accuracy. In the present study, eight fresh frozen human thoracic spinal specimens (C7-L1, mean age 54 ± 6 years) including the intact rib cage were loaded with pure bending moments of 5 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) with and without a follower load of 400 N. During loading, the relative motions of each vertebra were monitored. Follower load decreased the overall ROM (T1-T12) significantly (p < 0.01) in all primary motion directions (extension: −46%, left LB: −72%, right LB: −72%, left AR: −26%, right AR: −26%) except flexion (−36%). Substantial coupled motion was found in lateral bending with ipsilateral axial rotation, which increased after a follower load was applied, leading to a dominant axial rotation during primary lateral bending, while all other coupled motions in the different motion directions were reduced under follower load. On the monosegmental level, the follower load especially reduced the ROM of the upper thoracic spine from T1-T2 to T4-T5 in all motion directions and the ROM of the lower thoracic spine from T9-T10 to T11-T12 in primary lateral bending. The facet joints, intervertebral disc morphologies, and the sagittal curvature presumably affect the thoracic spinal coupled motions depending on axial compressive preloading. Using these results, the validation of numerical models can be performed more accurately.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Effects of axial compression and rotation angle on torsional mechanical properties of bovine caudal discs.

The intervertebral disc is a complex joint that acts to support and transfer large multidirectional loads, including combinations of compression, tension, bending, and torsion. Direct comparison of disc torsion mechanics across studies has been difficult, due to differences in loading protocols. In particular, the lack of information on the combined effect of multiple parameters, including axial compressive preload and rotation angle, makes it difficult to discern whether disc torsion mechanics are sensitive to the variables used in the test protocol. Thus, the objective of this study was to evaluate compression-torsion mechanical behavior of healthy discs under a wide range of rotation angles. Bovine caudal discs were tested under a range of compressive preloads (150, 300, 600, and 900N) and rotation angles (± 1, 2, 3, 4, or 5°) applied at a rate of 0.5°/s. Torque-rotation data were used to characterize shape changes in the hysteresis loop and to calculate disc torsion mechanics. Torsional mechanical properties were described using multivariate regression models. The rate of change in torsional mechanical properties with compression depended on the maximum rotation angle applied, indicating a strong interaction between compressive stress and maximum rotation angle. The regression models reported here can be used to predict disc torsion mechanics under axial compression for a given disc geometry, compressive preload, and rotation angle.

Degradation of bimorph piezoelectric bending beams in energy harvesting applications

Piezoelectric energy harvesting is an attractive alternative to battery powering for wireless sensor networks. However, in order for it to be a viable long term solution the fatigue life needs to be assessed. Many vibration harvesting devices employ bimorph piezoelectric bending beams as transduction elements to convert mechanical to electrical energy. This paper introduces two degradation studies performed under symmetrical and asymmetrical sinusoidal loading. It is shown that besides a loss in output power, the most dramatic effect of degradation is a shift in resonance frequency which is highly detrimental to resonant harvester designs. In addition, micro-cracking was shown to occur predominantly in piezoelectric layers under tensile stress. This opens the opportunity for increased life time through compressive operation or pre-loading of piezoceramic layers.

A design methodology for side wall failure of RHS truss X-joints accounting for compressive chord pre-load

This paper presents a design methodology for equal-width RHS X-joints failing by side wall buckling, with a particular focus on the effect of a compressive chord pre-load. A slenderness parameter is thereby defined based on the elastic local buckling stress of the side wall, idealized as an infinitely long plate under a patch loading transferred from the brace member in combination with a uniform chord pre-load. A Rayleigh-Ritz approximation is used to obtain a closed form solution. The proposed design equation is verified against finite element results over a wide range of wall slenderness values and is demonstrated to yield excellent predictions. Finally, a reliability analysis is performed using the first order reliability method (FORM) within the framework of both the Eurocode and the AISC Specification to ensure the proposed equation possesses the required level of safety. The proposed equation strongly outperforms the current CIDECT design rule for side wall buckling and also further extends the range of applicability to a wall slenderness ratio of up to 50.

Effect of follower load on motion and stiffness of the human thoracic spine with intact rib cage

Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive follower preload. However, dynamic mechanical testing using both the rib cage and follower load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive follower preloads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and follower preload. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a follower load, and (ii) neutral and elastic zone stiffness will be increased with a follower load. Eight human cadaveric thoracic spine specimen (T1–T12) with intact rib cage were subjected to 5Nm pure moments in lateral bending, flexion/extension, and axial rotation under follower loads of 0–400N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with follower load for every mode. Application of a follower load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing.